There is no getting away from the fact that Leon Kossoff’s early paintings are deeply weird, “deeply” being the operative word. These works are more like some form of sculptural relief than painting per se – they are certainly as far as you can get, physically and theoretically, from Clement Greenberg’s notion (contemporary with these works) of “ineluctable flatness.” The disturbing, gloomy, alienating mess that first confronts the viewer in these profoundly strange images finds a surprising kinship in the combines of Robert Rauschenberg, sharing with them an intrusive literalness. (Edward Kienholz also comes to mind.) The surprise in this commonality derives from the fact of the British painter’s humanism. His paintings depict the nude, family members, city streets—hardly the motifs of an art world iconoclast.

The show at Mitchell-Innes & Nash of ten paintings, mostly around five by four feet, made between 1957 and 1967, represents a first opportunity for Americans to see this important, intriguing body of work. And the ability to stand at the distances afforded by a brightly lit Chelsea gallery would change the way they are thought about for people who would have seen them when they were first exhibited, in London, in the markedly different kind of viewing space of the Beaux-Arts Gallery (Kossoff’s first dealer) in a musty mews off Berkeley Square.

Commensurate with their disconcerting depth, Kossoff’s early paintings are literally and metaphorically heavy. Color keeps up (or down, rather) with the weight of the paint in its somber, tonal, earthy murkiness. John Berger, in one of Kossoff’s earliest reviews, thought that his pictures “look as if they were made of coloured, solidified engine grease as put into a grease gun”. The defiant sweeps of brush or some cruder instrument through hefty slatherings of churned, predominantly brown, green and red paint resemble nothing so much as tire tracks on a sodden road.

The body language of the people depicted and, as far as they can be discerned, their facial expressions, also register heft. Father Seated in an Armchair no. 2 (1960) for instance, is an essay in lethargy. It is as if the sitter is as personally weighed down by the medium used for his portrayal as by the tribulations of post-war angst or austerity that might otherwise explain the leaden mood of the picture. The thought of the sagging heaps of paint seemingly slowly drying still before our eyes, almost half a century after being painted, adds to the metaphorical burden of the sense of aging and decay this melancholy image stirs.

“An essay in lethargy” – except it is painted with compelling energy, gusto, relish. This balance of observation and freedom from it is the paradox of Kossoff, the essence of his oddity. He recalls Francis Bacon’s dictum of “exhilarated despair,” which so sums up the School of London milieu of which Kossoff is part, along with such painters as Frank Auerbach and Lucian Freud. Along the lines of “exhilarated despair,” Kossoff excites oxymoronic responses of his own: frenetically slow, mesmerizingly alienating, gracefully heavy. For despite the initial impression of moroseness imparted by the muddy tones and turgid surfaces, once the eye adjusts to Kossoff’s personal language, these paintings reveal themselves as poignant and somehow capable, despite their initial gloom, of revealing nuance. Still, these early works stand in contrast to the comparative lyricism, the soft, luxuriant palette (still more tonal than chromatic) and delicate inner illumination that have come to mark Kossoff’s mature work. Kossoff emerged from these early gropings in the dark as an artist with an extraordinary ability to balance gravity and levity.

Leon Kossoff, Seated Nude no. 1 1963. Oil on board, 64 x 49 inches

He is an artist who has to draw a subject over an extended period before feeling ready to paint it, and yet, according to his own account, “I have never finished a picture without first experiencing a huge emptying of all factual and topographical knowledge.” His modus operandi finds a direct correlation in the experience of the viewer. These early images are laden with intimacy, of feeling and of observation, and yet to read them properly, to make sense of them beyond mere sensation, you have to get well away from them.

Up close and personal and without the benefit of the title, Seated Nude no. 1 (1963), for instance, reads more like an off-kilter landscape from Soutine than a nude. When you begin to see the figure she seems like an almost brutal caricature. But with requisite distance, anatomical credibility and a palpable sense of where the painter also stands in relation to the model come into focus. Ironically, it is at a distance that intimacy is possible, whereas in physical proximity the subject is remote.

Actually, to make proper sense of these pictures (assuming mimesis to be “the proper sense” of painting!) you should not only stand at some distance, you should also squint. For all their impasto and expressivity, you end up adopting a strategy like the one that works for Seurat, even though the latter’s highly finessed pointillism could not be more opposite in terms of sensibility and priorities to Kossoff.

This yoyoing viewing experience has aesthetic implications. It starkly dramatizes a contradiction in Kossoff between optic and haptic sensation, between seeing and touching. And as you move back and forth between a position that has you wallowing in the sheer, icky yet compelling stuff of the painted surface and a position that lets you read the image, you are forced – literally and spatially – to acknowledge another contradiction in Kossoff, between two competing definitions of realism.

Kossoff is realist in the traditional way of being grounded in closely witnessed – confronted – existential and social realities; but he also hits upon the realness of his paint surface, the obsessive, almost kinky thickness of his congealed mass of swirling, churning, mud-like matter. Walter Sickert advised artists to deal with “gross material facts,” meaning that they should prefer the scullery to the drawing room. In Kossoff, gross material fact is the form and the content, the medium and the message.